Boiler Feedwater Circuits
Measuring in Boiler Feed Water, Steam and Condensate
Boiler feedwater is the essential medium for all steam turbines. The feedwater is prepared by reverse osmosis and ion exchangers. Within the boiler, it is transferred to water steam to drive the turbines. Feedwater must be very pure to prevent any corrosion and incrustations within the turbine. A damage of the turbine is the most cost intensive accident within a conventional power plant.
Boiler Feedwater Circuits
Sector
3 Applications (1. Checking dissolved Oxygen DO, 2. Checking pH and Conductivity, 3. Checking Conductivity) at several measuring locations
Application
pH, Cond and DO
Measured Parameter
Key Requirements
- Low ion concentration
- Dual conductivity measurement to accurately calculate pH
Application Description
Criteria for the purity of the feedwater/condensate are conductivity, pH, and dissolved oxygen. In the schematic you find the typical measuring locations for dissolved oxygen, specific conductivity (SC), cation conductivity (CC), degassed acid conductivity (DAC) and pH. If the condensate return does not meet the specification, it needs to be discharged. pH and conductivity are the essential parameters of the boiler feedwater before entering the turbine.
In most cases, dual conductivity measurements are used to calculate pH and specific conductivity. pH and conductivity are the essential parameters of condensate (after passing the turbine). Usually dual channel conductivity measurements are used to calculate pH, specific conductivity (SC), cation conductivity (CA) and degassed acid conductivity (DAC).
Since CO2 from the air may enhance the conductivity, the degassed conductivity is an important criterium for the purity.
Requirements of Application
The challenge is based on the low ion concentration of the medium, which requires a double conductivity measurement to accurately calculate the pH value.
Why Knick ?
The challenge of the application is the low ion concentration and typically amine is dosed for avoiding corrosion. Amine dosing based on conductivity is not easily possible – pH monitoring is also required, which is difficult due to the low ion content. Therefore, a better approach is to accurately calculate pH based on the dual conductivity measurement. Stratos Multi is the perfect fit for this application, as the dual conductivity measurement can easily be combined with a DO measurement for ideal process monitoring.
Solution - Product Highlight
Features
- Modern easy to operate transmitter in a lot of languages
- Dual input for conductivity to calculate pH in addition to conductivity
- Option for a 3rd DO sensor
- 3 measuring points in one
- Modern fieldbus Communication
Customer Benefit
- Cost-effective solution 3 in one
- Easy remote calibration by using the MemoSuite software
- HART, Profinet, Ethernet IP with predictive maintenance.
(for Application 1)
Features
- Luminescence technology (optical)
- Range: 4 ppb to 25 ppm
- Digital communication to meter
- Maintenance by basic cleaning or replacement of cap
- No electrolyte required
Customer Benefit
- High accuracy
- Low maintenance
- Easy to calibrate
2-Electrode Conductivity Sensor SE604
(for Application 2 and 3)
Features
- 0.04 … 1,000 μS/cm
- Stainless steel 1.4435, PEEK insulator
- Up to 120 °C and 25 bar
- Available with Memosens technology
- Easy cleanability due to removable outer electrode
Customer Benefit
- Lowest measuring range
- Suitable for high pressures and temperatures
- Remote calibration by Memosens protocol
Features
- Robust flow through fitting in stainless steel
- Various sensor and process connections
Customer Benefit
- Accurate measurement
- Suitable for moderate temperatures and high pressures